The present invention relates to carburetor for internal combustion engines and especially to an improved throttle valve and method of attaching an improved throttle valve to an existing carburetor.
In a typical internal combustion engine, hydrocarbon fuel and air are mixed and metered in a carburetor on the intake manifold of the engine. Each engine has a carburetor tailored to the individual engine requirements, but most carburetors operate in the same manner. Most carburetors have fixed venturies, even though a few engines utilize variable venturi carburetors and many engines use fuel injection for direct injection of the fuel into the combustion chamber. In a typical carburetor, the hydrocarbon fuel is supplied by a pump to a float controlled reservoir. During cruise conditions, fuel is drawn through jets by the pressure drop created by the increased velocity of the air flow through the venturi. This air flow is normally controlled by a butterfly or throttle plate valve. During other phases of operation, such as idle, acceleration, deceleration, various other mechanisms come into play, such as idle jets, acceleration pumps and power valves. These functions are controlled by changes in manifold and venturi vacuum valves. Carburetor designs are aimed at smoothing out transition between these various operating conditions to eliminate stumbling, hesitation and excessive lean or rich spot fuel delivery. The overall result is still far from ideal, in that there is still too much unused fuel. When atomized fuel reaches the throttle valve plate in normal driving range, the slope of the plate across the throat causes uneven distribution. Most of the fuel, including idle port and transfer slots supplies, and about half of the air, flow through the lower throttle opening while considerably less fuel and about half of the air goes through the upper throttle opening. This poor mixing arrangement is never corrected, so that when the engine is under heavy load or rapid acceleration, fuel is wasted. As the manifold vacuum falls, air flow velocity decreases through the venturi causing larger fuel drops to be formed thereby decreasing the effectiveness of the fuel-air ratio. This is compensated for by the carburetor by adding more fuel through the accelerator pump and pump valves, which dump raw gasoline into the air stream increasing the liquid collecting in the intake manifold. Because of the location of the idle holds and slots at the edge of the throttle plate, there is an inefficient mixing of the idle gasoline even with the high velocity air flow during idle.
The efficient distribution of the fuel-air mixture to the combustion chambers is also hurt by manifold designs, which sometimes result in an uneven distribution of fuel, from cylinder to cylinder and in adjustments to carburetors made to meet federal exhaust emission standards, by setting the carburetors slightly on the rich side of the most efficient operation of the engine where it has been shown that emissions decrease. To meet federal standards, timing may be retarded, fuel mixture varied, manifolds heated, valve timing changed and air injected into the exhaust manifold and catalytic converters have been added to the vehicles.
Typical prior U.S. patents which have throttle valves with altered shapes may be seen in U.S. Pat. No. 3,814,389, for a carburetor having a modified butterfly valve to block the lower most idle bypass opening; and in the Eversole, et al., U.S. Pat. No. 3,778,038, which uses a cone shaped valve to more fully divide fuel particles in the air. The Holzbaur U.S. Pat. Nos. 4,079,718 and 4,064,847 actually distribute fuel through a throttle valve.
An aim of the present invention is to provide an easily modified throttle valve to streamline the throttle valve with spherical segments to improve the flow and atomization of the fuel-air charge for the combustion chamber.